Ariane 4

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In 1982, the Ariane 4 programme was approved by the European Space Agency (ESA). Drawing heavily upon the preceding Ariane 3, it was designed to provide a launcher capable of delivering heavier payloads and at a lower cost per kilogram than the earlier members of the Ariane family. The Ariane 4 was principally an evolution of the existing technologies used, as opposed to being revolutionary in its design ethos; this approach quickly gained the backing of most ESA members, who funded and participated in its development and operation. Capable of being equipped with a wide variety of strap-on boosters, the Ariane 4 gained a reputation for being an extremely versatile launcher.[not verified in body]

Once in service, the launcher soon became recognised for being ideal for launching communications and Earth observation satellites, as well as those used for scientific research. During its working life, the Ariane 4 managed to capture 50 per cent of the market in launching commercial satellites, soundly demonstrating Europe's ability to compete in the commercial launch sector.[1] In February 2003, the final Ariane 4 was launched; Arianespace had decided to retire the type in favour of the newer and larger Ariane 5, which effectively replaced it in service.

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In 1973, eleven nations decided to pursue joint collaboration in the field of space exploration and formed a new pan-national organisation to undertake this mission, the European Space Agency (ESA).[2] Six years later, in December 1979, the arrival of a capable European expendable launch system was marked when the first Ariane 1 launcher was successfully launched from the Guiana Space Centre at Kourou, French Guiana.[3] The Ariane 1 soon became considered to be a capable and competitive launcher in comparison to rival platforms offered by the Soviet Union and the United States of America, and it was quickly followed by improved derivatives in the form of the Ariane 2 and Ariane 3. By early 1986, the Ariane 1, along with the Ariane 2 and Ariane 3, had become the dominant launcher on the world market.[4]

In January 1982, the ESA issued its authorisation for the development and construction of the Ariane 4; the development programme had the stated objective of increasing the usable payload by 90 per cent.[5] The Ariane 4 would be a considerably larger and more flexible launcher that the earlier members of its family, being intended to compete with the upper end of launchers worldwide. In comparison, while the Ariane 1 had a typical weight of 207 tonnes and could launch payloads of up to 1.7 tonnes into orbit; the larger Ariane 4 had a typical weight of 470 tonnes and could orbit payloads of up to 4.2 tonnes.[6] Work on the Ariane 4 was substantially eased via drawing heavily on both the technology and experiences gained from producing and operating the earlier members of the Ariane rocket. The total development cost for the Ariane 4 was valued at 476 million European Currency Units (ECU) in 1986.[5]

Posed with the requirement to produce a rocket with substantially greater thrust, the design team considered various approaches to achieve this.[7] One concept studied had involved the addition of a fifth engine to an enlarged first stage of the Ariane 3, but was found to involve a very high level of redesign work to achieve this; instead, the first stage was elongated to hold 210 tonnes of propellant instead of the 145 tonnes present on the Ariane 3. While the second and third stages remained identical to the Ariane 3, a range of strap-on boosters were developed to be applied to the type, designed to gradually increase the rocket's payload capacity.[7] Overall, the Ariane 4 was 15 per cent smaller than the Ariane 3.[8]

In effect, the Ariane 4 was an improved and developed derivative of the earlier Ariane 3, primarily differing through the application of various solid-fuelled and liquid-fuelled boosters, the latter being the only all-new design feature of the Ariane 4; at this point, the practice of using liquid boosters was uncommon, having only previously been used in the Chinese space program.[7] Another innovation of the Ariane 4 was the dual-launch SPELDA (Structure Porteuse Externe de Lancement Double Ariane) fairing.[8] This had the function of allowing a pair of satellites, one placed on top of the other; several different SPELDA nose fairings could be installed, including normal and extended models. The SPELDA was considerably lighter than its predecessor; the guidance system also used much more accurate ring laser gyroscopes.[8] According to aviation author Brian Harvey, the advances present in the design of the Ariane 4 represented a conservative and evolutionary, rather than revolutionary, philosophy.[8]

In conjunction with the development of the Ariane 4 itself, a new purpose-built launch preparation area and launch pad for the rocket, collectively designated as ELA-2, was constructed at the Guiana Space Centre to service the Ariane 4 and provide a launch rate of 8 launches per year (this feat was near-unprecedented for a single large rocket, other than within the Soviet Union).[10] Unlike the earlier ELA-1 which had been used for the previous members of the Ariane family and other rockets, preparation activity for the rocket would be performed in a purpose-built 80-meter tall hall rather than on the pad itself; the completed rocket was then be transported using a specially-designed railway to slowly traverse from the hall to the launch pad, taking one hour. This railway provided the additional benefit of enabling faulty rockets to be withdrawn from the pad and be substituted for relatively quickly.[7]

On 15 June 1988, the first successful launch of the Ariane 4 was conducted.[8] For this first test flight, it was decided to fire the most powerful version of the rocket, designated 44LP, equipped with four main engines, two solid boosters and two liquid boosters; it was also furnished with the multi-satellite SPELDA fairing. 50 seconds after take-off, the solid boosters would be expended and be detached in order to reduce the rocket's weight.[8] 143 seconds after take-off, the liquid boosters also detached, further lightening the vehicle. The maiden flight was considered a success, having put multiple satellites into orbit.[8]

For the V50 launch onwards, an improved third stage, known as the H10+, was adopted for the Ariane 4.[11] The H10+ third stage featured a new tank, which was 26 kg lighter, 32 cm longer, and contained 340 kg more fuel, which raised the rocket's overall payload capacity by 110 kg and increased its burn time by 20 seconds.[11]

Even prior to the first flight of the Ariane 4, development of a successor, designated as the Ariane 5, had already commenced.[12] In January 1985, the Ariane 5 had been officially adopted as an ESA programme. It lacked the high levels of commonality that the Ariane 4 had with its predecessors, and had been designed not only for launching heavier payloads of up to 5.2 tonnes and at a 20 per cent cost reduction over the Ariane 4, but for a higher margin of safety due to the fact that the Ariane 5 was designed to conduct manned space launches as well, being intended to transport astronauts using the proposed Hermes space vehicle.[13] Development of the Ariane 5 was not without controversy as some ESA members considered the more mature Ariane 4 to be more suited for meeting established needs for such launchers; it was for this reason that Britain chose not to participate in the Ariane 5 programme.[14] For some years, Ariane 4 and Ariane 5 launchers were operated interchangeably; however, it was eventually decided to terminate all Ariane 4 operations in favour of concentrating on the newer Ariane 5.[15]

The Ariane 4 was the ultimate development from the preceding members of the Ariane rocket family. Compared with the Ariane 2 and 3, the Ariane 4 featured a stretched first (by 61 per cent) and third stages, a strengthened structure, new propulsion bay layouts, new avionics, and the SPELDA (Structure Porteuse Externe de Lancement Double Ariane) dual-payload carrier. The basic 40 version did not employ any strap-on motors, while the Ariane 42L, 44L, 42P, 44P, and 44LP variants all used various combinations of solid and liquidboosters. Originally designed to place 2.0–4.2 tonne payloads in geostationary orbit, the six Ariane 4 variants, aided by strap-on boosters, enabled the launch of payloads in excess of 4.9 tonnes on several occasions.[citation needed] According to Harvey, the Ariane 4 launcher had reduced the launch costs per kilo by 55 per cent in comparison to the original Ariane 1.[8]

The rocket was used in a number of variants - it could be fitted with two or four additional solid (PAP, propulseurs d'appoint à poudre) or liquid fueled booster rockets (PAL, propulseurs d'appoint à liquide). The launcher included a satellite payload carrier system called Spelda (Structure porteuse externe de lancement double Ariane, French for external carrying structure for Ariane double launches) for launching more than one satellite at a time. The rocket captured nearly 60% of the world's commercial launch services market, serving both European and international clients.[16] Atop the third stage was a vehicle equipment stage which housed a computer that performed various functions, including sequencing, guidance, control, tracking, telemetry and an explosive-based self-destruct.[8]

The Ariane 4 AR 40 was the basic version, with three stages: 58.4-m high, a diameter of 3.8m, a liftoff mass of 245t and a maximum payload of 2100 kg to GTO or 5000 kg to low Earth orbit (LEO). Main power was provided by four Viking 2B motors, each producing 667 kN of thrust. The second stage was powered by a single Viking 4B motor, and the third stage was equipped with an HM7-B liquid oxygen/liquid hydrogen motor. The Ariane 4 AR 44L, which was outfitted with the maximum additional boost of four liquid fuel rocket strap-ons, was a four-stage rocket, weighing 470t and capable of transferring a payload of 4730 kg to GTO, or alternatively 7600 kg to LEO.

In June 1988, the inaugural flight of the Ariane 4 occurred, which was a success. Since then, Ariane 4 has flown 116 times, 113 of which were successful, yielding a success rate of 7001974000000000000♠97.4%. On 22 February 1990, the first failure occurred during the eighth Ariane 4 launch: the rocket exploding 9 km above Kourou.[17] Following an exhaustive investigation, which found that an unknown foreign object had obstructed a water line, a total of 44 modifications were recommended to prevent any reoccurrence. The following 26 launches were all completed successfully thereafter.[11]

The system became the basis for European satellite launches with a record of 113 successful and three launch failures. Ariane 4 provided a payload increase from 1700 kg for Ariane 3 to a maximum of 4800 kg to geostationary transfer orbit (GTO). The record for Ariane 4 to GTO was 4946 kg.[18]

On 15 February 2003, the final launch of Ariane 4 rocket occurred, placing Intelsat 907 into geosynchronous orbit.[19] Arianespace had decided to phase out the Ariane 4 launcher in favour of the newer heavy-lift Ariane 5 rocket, which had already been in service for some years. In 2011, the medium-lift Soyuz ST complemented the offering of launch vehicles from the Guiana Space Centre. Spacecraft launched by the Soyuz reused the payload platform and dispenser which had been originally designed for the Ariane.[20]